As far as the electronics upgrade goes, my '81 series I is still quite a bit quieter than most other basses on the planet (the pots are a bit scratchy), even if it is noisier than a new Alembic.  It's perfectly quiet in any properly-wired studio space.  I would hardly consider an upgrade as being critical enough to thwart the purchase of an otherwise beautiful bass...
John

John - a quick tip. Mica has suggested in the past that 'scratchy pots' can usually be remedied simply by rotating them back and forth a bunch of times. Worked for me recently (on a non-Alembic), so it's worth a try.